3.0L hard starting when warm

[Dremmick1985]

I have a 2005 mercrusier 3.0L with TKS carb. The boat starts instantly when cold but starts really hard when warm seems like its flooding itself.

I replaced the dist cap , rotor, spark plugs, spark plug wires, and fuel filter.

 

[santino44]

And I have the same.

 

[Bondo]

I have a 2005 mercrusier 3.0L with TKS carb. The boat starts instantly when cold but starts really hard when warm seems like its flooding itself.

I replaced the dist cap , rotor, spark plugs, spark plug wires, and fuel filter.

Ayuh,..... Welcome Aboard,...... How did ya figure it's floodin',..??
Did ya pull the spark plugs, 'n find 'em wet,..??
Did it start when ya move the throttle to Wot,..??

 

[santino44]

On my boat, moving the throttle forward a little will give the engine a better start.

 

[Dremmick1985]

Ayuh,..... Welcome Aboard,...... How did ya figure it's floodin',..??
Did ya pull the spark plugs, 'n find 'em wet,..??
Did it start when ya move the throttle to Wot,..??

Just assumed it was flooding. I had to move the throttle to WOT in order for it to start which took several attempts and once it started it seems like the engine was stumbling.

 

[alldodge]

The TKS carb has a module which when the engine warms up, the module closes off the port which gives the motor more fuel. The motor needs more fuel when cold but is flooding when warm.

Check the 20 amp fuse, it provides 12V full time. Motor is stated and oil pressure builds which applies a ground to the other side of the module. The module slowly closes off the extra fuel.

When motor is warmed up the Temp switch closes. and also connects a ground. When motor stops, the Temp switch maintains the ground to keep the module closed. It will stay that way until the motor goes cold

 

[Searay205]

Maybe vapor lock. Does your carburetor have a thick phenolic gasket under it to prevent the hot manifold from boiling the gas out after sitting for awhile with engine off? Mine had that issue, option 1 was just crank the crap out of it, option two was when anchoring for awhile push the throttle all the way forward after you shut it off so when you start it the throttle plate is wide open. option 3 and my favorite use some ether AKA starting fluid. Always loved the smell and always worked perfect...

 

[Dremmick1985]

The TKS carb has a module which when the engine warms up, the module closes off the port which gives the motor more fuel. The motor needs more fuel when cold but is flooding when warm.

Check the 20 amp fuse, it provides 12V full time. Motor is stated and oil pressure builds which applies a ground to the other side of the module. The module slowly closes off the extra fuel.

When motor is warmed up the Temp switch closes. and also connects a ground. When motor stops, the Temp switch maintains the ground to keep the module closed. It will stay that way until the motor goes cold

View attachment 346431

Should there always be 12V going into the module with the engine off and key on even when the engine is warm?

 

[Dremmick1985]

Maybe vapor lock. Does your carburetor have a thick phenolic gasket under it to prevent the hot manifold from boiling the gas out after sitting for awhile with engine off? Mine had that issue, option 1 was just crank the crap out of it, option two was when anchoring for awhile push the throttle all the way forward after you shut it off so when you start it the throttle plate is wide open. option 3 and my favorite use some ether AKA starting fluid. Always loved the smell and always worked perfect...

I would have to look. Are you referring to a cork gasket.

 

[Dremmick1985]

I would have to look. Are you referring to a cork gasket.

 

[alldodge]

Should there always be 12V going into the module with the engine off and key on even when the engine is warm?

One side will always have 12V on it, key ON or OFF. The other side is where it gets turned ON with a ground. Think of it like the switch is on the ground side and not the hot side

 

[Dremmick1985]

it only turns on when the engine is warm? The end cap felt hot yesterday when trying to set timing

 

[alldodge]

it only turns on when the engine is warm? The end cap felt hot yesterday when trying to set timing

No,
Motor starts cold, oil pressure builds and connects TKS module to a ground

With ground applied the TKS starts to heat up and close off extra fuel

After a few minutes the module will close off the extra fuel

Once engine temp heats up the temp switch connects module to ground to keep module closed

When motor is shut off the temp switch keeps the module connected to ground to keep extra fuel closed off

If motor stays off long enough the temp switch will open and remove the ground, which allows the TKS module to cool down and open port back up

 

[Dremmick1985]

No,
Motor starts cold, oil pressure builds and connects TKS module to a ground

With ground applied the TKS starts to heat up and close off extra fuel

After a few minutes the module will close off the extra fuel

Once engine temp heats up the temp switch connects module to ground to keep module closed

When motor is shut off the temp switch keeps the module connected to ground to keep extra fuel closed off

If motor stays off long enough the temp switch will open and remove the ground, which allows the TKS module to cool down and open port backho

How can I verify that the module is closed when trying to start a warm engine?

 

[alldodge]

There is nothing visual you can just look at. The plunger is inside the carb. With the motor running there will be some extra hissing heard if its still opened.

The module can be tested by removing and apply 12V and after about 8 minutes it will move out (cold 7/8 full out 1 1/4). If the motor is all warmed up the module could be removed and measured

 

[Dremmick1985]

My plunger only extended 30.5mm

 

[alldodge]

Does list approximate so unsure if 1.25mm is enough to cause an issue. Before replacing I would determine which lead has 12V full time, then connect a voltmeter to the other side. Start the motor and it should go from 12V to 0V when the oil pressure switch closes.

Run the motor long enough to get it at temp. Shut the motor OFF and see if the point stays at 0V by the temp switch

 

[Dremmick1985]

Does list approximate so unsure if 1.25mm is enough to cause an issue. Before replacing I would determine which lead has 12V full time, then connect a voltmeter to the other side. Start the motor and it should go from 12V to 0V when the oil pressure switch closes.

Run the motor long enough to get it at temp. Shut the motor OFF and see if the point stays at 0V by the temp switch

Sorry for all the questions. Are you referring to the 12volt lead going into the tks module? What do you mean by the other side? the other wire going into the module? Doesn't the oil pressure switch provide a ground path for the TKS module once it senses oil pressure then once up to temp the temp switch provides the ground? When the engine is turned off hot shouldn't there sill be 12v going to the module to close of the fuel?

 

[alldodge]

12V is always present on one lead of the TKS module
The module is turned ON by a ground being applied to the other TKS lead

If there is no ground (motor cold, key not on) you should read 12V on both leads. Once motor starts the oil pressure switch grounds one lead of the TKS

The Temp switch is there to keep a ground on one side of the TKS so it does not cool down and open the extra fuel port again. The TKS draws very little current so it being ON with motor OFF is not an issue. If the motor stays off long enough, the Temp switch opens up and removes the ground thereby removing the ground and allowing the TKS to open

 

[Dremmick1985]

Whats the easiest way to measure the leads going into the module? Pierce the wire sheathing?